Sunday, 22 March 2009

The Egrets have landed

Rather incongruously the 'species of the day' yesterday was Cattle Egret. 22 of them. These small white herons have done very well following man and his cattle farming around the world. They naturally colonised the Americas after about 100 were swept across the Atlantic in a storm and found cattle ranches in Brazil rather to their liking (presumably birds had made the crossing before to find that rainforest didn't suit them). From there they have spread north and south and are now a familiar bird in North America. What this does mean is that the entire american population is descended from a group with possibly not the most top-notch navigation skills, and the species is very dispersive anyway. Unfortunately there is nothing for them out here and we can't keep them on board until the Falklands (where they don't survive well anyway). We've left them be and several have fallen into the sea exhausted. Sad, but that's nature and where they'd be if we weren't providing a relatively dry platform. There have also been a number of dead penguins. All food for the Giant Petrels, some of which have been so full that they couldn't fly (they are also in wing moult which doesn't help) Otherwise there have been a few proper seabirds around (the kind that can land on and drink seawater, which are two key necessary traits for birds out here) and, increasingly inevitably, more Fin Whales (10 blowing as we stopped for the latest CTD)

Cattle Egret sheltering under Sooty, one of the Ship's work boats

Another under some stairs

It's been a bad day! Unfortunately these birds won't survive. Young birds (as these probably are) disperse after they leave their parents, searching for suitable habitat. In the case of Cattle Egrets this would have been important in natural conditions when they had to find the new forest clearings where they could feed on insects disturbed by large animals. Now, with cattle farms being less ephemeral it is of less use, but has allowed them to spread with man and his cows.

Cape Petrel, a common species that hangs around the ship

Antarctic Fulmars

Cattle Egrets behind the incubators. The incubators are for testing the relative effects of iron addition and light availability on phytoplankton growth. Iron is the chemical fertiliser needed to stimulate growth of Southern Ocean algae as it is naturally present in very low concentrations. In large part this is because it is very insoluble when it reacts with oxygen. There is plenty of excess oxygen in the oceans, but only because of the algae in the first place billions of years ago. The law of unitended consequences strikes again.

1 comment:

Helene; Florent; Matthias said...

Hi Hugh,
It is nice to read you again! How long are you at sea for?
Everything is fine for us in our urban jungle of New Jersey, we are getting used to it I guess ;-)
Take care and keep the posts going!